An air cycle HVAC system typically employs a compressor, a heat exchanger, and an expander in an open loop system to generate cold air. These air cooling systems are currently commonly found in aircrafts. The compressor receives ambient air and pressurizes the same causing the air to become hot. The heat exchanger dissipates some of the heat in the air exiting the compressor. The air then flows through the expander which removes work and brings the air back to atmospheric pressure, resulting in cold air which can be supplied to the passenger cabin.
In such an air cycle system, there may be times when additional air is needed to increase the total air flow of the system. Generally, prior solutions have been to provide a secondary air flow of ambient air that is immediately mixed with the cold air from the air cycle to meet the demands on the system. Unfortunately, the secondary flow of ambient air is relatively humid, and may condense on the interior of the cockpit, such as on the inside surface of the windows. Further, the two separate air streams will result in hot and cold stratification in the air distribution system. Accordingly, there exists a need to provide an air cycle system that can provide an increased total air flow of the system while preventing unwanted condensation and hot and cold stratification.